Nutating mechanism



March 15, 1949.

INVENTOR.

fgjammf.

J. l. HERZLINGER 2,464,394

Patented Mar. 15, 1949 Radio Corporation of America.,

fof Delaware a 'wrp'oration This invention relates to vimprovements [in mechanisms for effecting a 'changein'theaxis of 'a rotating body and will "be described a's applied to a system wherein the rotating body moves an .antenna of a radar or'like installation.

In certain ultra-high frequency pulse `systems for the communication Vof intelligence, n'otably in so-called target-tracking radar vand analogous (position determining) systems, i1? has heretofore been'proposedto 'employ ahollow rodlike member or waveguide as the 'antenna 'and vto subject Athe said member 'to nutatiorn lselectively, 1at 'a small angle, a 'large 'angle or va spiral be- 'tween'the two angles, forpurposes of electrically exploring or scanning the ether.

The mechanisms employed for selectively 4vimparting such processional movements 'to Aan antenna have heretofore been v,more complex and cumbersome than is desirable `in 'apparatus idesigned for .use in air-craft and other mobile in- Stallations.

Accordingly, the 'principal object 'df 'the pres- ,ent invention 'is tto provide va reliable yet simple automatic-means for nutating 'an antenna, .selectively, at a small angle, a large angle 'or 'a spiral between the 'two angles, and one which dispenses with the complicated 'clutches andrelays heretofore employed in effecting the changeover.

The foregoing and 'other objects are achieved in .accordance with the invention bythe provision of a novel centrifugally controlled mechanism which operates, in response to 'a change inspeed of the driving motor, to eiect hthe desired precession or change in the orientation of the Aaxis of the driven member.

'The invention will be :described Ain connection with the accompanying 4drawing wherein:

Fig. l is a longitudinal View, partly vin section'of a motor Adriven nutating antenna -system incorporating `a centrifugally lactuated mechanism, within the invention, for controlling the angle 'o f nutation.

Fig. 2 is a similar View, with the motor omitted, showing how the vcentrifugal control of 'the invention operates to increase the rangle yof nutation or cone of precession of the antenna and Fig. 3 is a fragmentary view 'of'thecentrifugal'l control and including a 'gear system `and switch lfor continuously varying the displacement ofthe axis of precession of the antenna.

As previously indicated the purpose of `the mechanism shown in vFigs'l and'2'is tovnutatethe movable antenna or'wave guide A 'about-a point l? at a small angle @such-#as 1f degree '(Fig. Ji) and,

selectively, at some large angle p (Fig. 2) such as ..6 degrees. As will hereinafter more fully appear this precess'ion' .or change in the direction v,of 'the .axis `:-:r of the movable antenna Af'is achieved 'by changing the speed of the motor 'M from, say, 1800 toSay, 9.00 revolutions per min.- ute.

(Having regard to the electro-mechanical targetf'trackingproblems involved it is usually eX- pedient to use the higher motor speed in achiev.- ing the smaller angle of Vmutation.)

vAs is conventional, the hollow-rod-like antenna A is supported adjacent to its inner endupona gimbal `consisting of a ring or sleeve 2 in which the antenna can 'turn on an axis through the diameter oi 'the ring, while the ring itself is so pivo'ted ona tiltable support, indicated generally at ij, 'that it can 'turn about a diameter at right angles to 'the first mentioned diameter. As vis lilewise conventional, the pulses or high frequency energy to'be broadcast "by the antenna A are supplied thereto by a stationary wave guide Shaving a convex outlet port (or choke joint) 'lijd which abuts thesimilarly curved inlet port "8a of the antenna Without interfering with the nuetation of thelatter.

It will be 'observed that the gimbal ring or 'sleeve '2 within'which the antenna is mounted is 'provided with van integral extension I0 which terminates in a `bushing l2 'Within which a shaft 'His J'Ourn'aledfor rotation, Since the part I'0 'is "integral withthe gimbal 'ring 2 and is supported only Von the tiltable support 4 it is yapparent that anyforc'e applied vto the outer (i. e. left) end of 'the shaft I4 Vwhich results in movement of its axis `of `spin (sothat the `said axis traces a cone cf'precession about point P as Vthe apex) will subject the `antenna A Ito nutation so that it too traces a cone, the apex of Whichisjthe point P.

lIt should 'be Ynoted. thatthe antenna does not spinabout its axis "when subject to the described force, because the rotary movement of thedriven shaft lli is not transmitted beyond the bearing lfzwithinwhichthe said shaft is journaled. The movement to which the antenna A is `subjected can 'best bevisua'lized by holding'a mechanical pencil attits point, inthe Vleft hand, with the clip on the pencil toward the'observer andthen, with the righthand, moving the free end of the pencil in 'a circle,-keeping the -clip vfacing the observer 'at' alltimes, Iand the left hand stationary.)

*The apparatus of Figs. 1 and 2, as thus far described is 'of af-lnown type and the present invention is-not concerned with-the foregoing details ofconstruction lexcept in so far as the said apparatus is capable of being driven by the novel centrifugally controlled mechanism herein described. This mechanism comprises a bell crank assembly comprising two levers IE and I8 joined at one` end by a pivot 2B and pivotedly connected at their fulcrums, Ia and Ia to the shaft 22 of motor M. As shown more clearly in Fig. 1 the motor shaft 22 is hollow and has a rod 24 mounted for axial movement within its bore. It is normally biased to the left, as viewed in Fig. 1, by a spring 25 which exerts its force against a piston 28 on the said end of the rod. The piston 28 and its spring 26 operate within an oil-filled cylinder 3Q so that the assembly comprises a dash-pot which clamps the later described axial movement of the rod 2li. The cylinder 30 is threaded on, or otherwise aixed to, the motor shaft 22 and hence rotates therewith. Suitable stops 32 and Sli within the shaft 22 limit the degree of axial movement of the rod 2li with respect to the said shaft.

The opposite end of the axially movable rod 2G is connected by a short link 36 to the pivot 2i) which joins the adjacent ends of the two levers I6 and I8. The free end of one of the levers, i. e. lever It, is provided with a bearing in the form of a stud-shaft or pin 38 which is slideably splined for axial movement in the bifurcated end of the tiltable driven shaft Iii which is supported by the gimbal 2 upon which the antenna A is mounted. The free end of the other lever is provided, in accordance with the invention, with a counterweight 40.

The center of gravity of the nutating system controlled by the counterweight 4I) is at the point of the moments of the counterweight 4! about the fulcrum IBa. of the lever I8 and the moment of the nutating mass about the fulcrum Ia of the other lever I6, exerts a force at the central pivot 2F) which is greater than the biasing force of the spring 26 acting on the piston 28. Hence, r

the piston rod 255 moves to the right, as shown in Fig. 1, to a position whereat its axial movement is arrested by the stop 32. This axial movement of the rod 2i is applied by the link 36 to the lever IE so that the said lever pivots counterclockwise on its fulcrum Iia. Thus the stub shaft or pin 38 on the outer end of this lever I6 applies a tilting force to the driven shaft I4 and the said shaft exhibits a slight (say, l degree) nutant or nodding movement about the point P. As previously set forth, this change in the orientation of the axis of the driven shaft I4 with respect to the xed axis of rotation of the driving shaft 22 is transmitted by the grnbaled support 2 to the antenna A which thus exhibits the same small angular degree of nutation about point P, as the said shaft I4.

In order to increase the angle of nutation of the driven shaft I4 (and hence to increase the diameter of the cone traced in space by the antenna A) it is merely necessary to operate the motor M at its second or lower speed, in this case 900 R. P. M. When the speed of the motor is thus reduced the force of the spring 26 is greater than the centrifugal force exerted by the counterweight 4D and the nutating mass I4 and A, hence the rod 24 is pulled against the right hand stop 34. As shown in Fig. 2 this movement of the rod 24 to the left pulls the pivot 20 in the same direction and imparts a clockwise movement to the bell crank I5 and the desired additional degree of tilt to the driven shaft I4. It may be pointed out that the system stays in dynamic balance at both speeds, and during the changeover, since the center of gravity T and the counterweight I0 move in the same direction with respect to the axis of rotation of the driving shaft 22.

When it is necessary or expedient to change the angle of precession, continuously, between the small angle of Fig. 1 and the large angle of Fig. 2, suitable means may be provided for changing the speed of the motor M. Thus, as indicated in Fig. 3, the speed of the motor may be controlled by a switch 42 under the control of a cam I4 which is driven by pinion 46 on the motor shaft 22 through a driven gear 43 on the cam shaft 50. Here the counterweight 4U operates, as before, to nutate the driven shaft I4 at a small angle at the higher motor speed and at the larger angle at the lower speed. Hence, when the speed of the motor is changed, periodically, the free end of the antenna will describe a spiral, between the said angles, in space.

It will now be apparent that the present invention provides a reliable yet simple centrifugal means for nutating an antenna, or other rod like structure, selectively, at a small angle, a large angle, or a spiral between the two angles.

What is claimed is:

, 1. In apparatus of the character described, a driving shaft mounted for rotation about a fixed axis, a driven member mounted to permit of nutation about -a point substantially in register with said axis, means connecting said shaft and said member in driving relation, and centrifugal means responsive to the speed of rotation of said driving shaft for controlling the angle of nutation of said driven member.

2. The invention as set forth in claim 1 and wherein said driven member comprisesa rotatable shaft.

3. The invention as set forth in claim 1 wherein said driven member comprises a rod-like antenna and wherein said connecting means between said driving shaft and said antenna includes a nutant driven shaft.

4. In apparatus of the character described, a driving shaft mounted for rotation at different speeds about a fixed axis, a driven shaft having an axis of rotation and mounted to permit of changes in the orientation of its said axis with respect to said fixed axis, means connecting said shafts for rotation about their respective axes, and centrifugal means responsive to said diierent speeds of said driving shaft for changing the orientation of said axis of said driven shaft with respect to said xed axis.

5. The invention as set forth in claim 4 including means for periodically changing the speed of rotation of said driving shaft, whereby the axis of said driven shaft generates a cone of precession in changing its orientation with respect to said fixed axis.

6. In apparatus of the character described, a hollow rotative driving shaft containing a rodlike member mounted for axial movement therein, a plurality of bell-cranks pivotedly connected each at one end to one end of said axially movable rod and each at its fulcrurn to said driving 5 shaft, a driven shaft supported at one end for nutation and connected at its opposite end in torque transfer relation with respect to said driving shaft through one of said bell-cranks, and a counterweight carried by the other of said beilcranks and responsive to rotation of said driving shaft for moving said rod-like member axially whereby to. apply a nutating force to said driven shaft through the other of said bell cranks.

7. The invention vas set forth in claim 6 and wherein the center of gravity of said driven shaft is diametricaily opposite said counterweight.

JOSEPH I. HERZLINGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,407,275 Hays Sept. 10, 1946 2,407,310 Lundy et a1 Sept. 10, 1946 2,408,825 Varian et ai. Oct. 8, 1946 2,409,183 Beck Oct. 15, 1946 2,410,827 Langstroth et a1. Nov. 12, 1946 2,412,631 Rice Dec. 17, 1946 2,415,680 Hoyt Feb. 11, 1947 2,419,556 Feidman Apr. 29, 1947 

